Object distance measuring device in camera

ABSTRACT

An object distance measuring device in a camera, including an active object distance measuring mechanism for emitting measuring light toward an object to be photographed and receiving the measuring light as reflected by the object to detect the object distance is provided. A measuring zone is provided in a finder to indicate a measuring position at which the measurement of the object distance by the active object distance measuring mechanism is effected. A device is provided for varying the position of the measuring zone in the finder, and a device for varying the direction of the emission of the measuring light by the active object distance measuring mechanism in accordance with the varied position of the measuring zone is also provided.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a measuring device for measuring adistance of an object to be photographed from a camera with which it isbeing photographed. More precisely, it relates to an object distancemeasuring device in a camera having an active autofocusing system withan infrared LED which emits light for measuring the distance of theobject to be photographed.

2. Description of the Related Art

In a camera having an active autofocusing system with an infrared LED,an infrared light for measuring distance is emitted toward the objectfrom the infrared LED provided in the camera body. This measuring lightis then reflected by the object and received by a light receiver on thecamera body, which detects the object distance in accordance with themeasuring light. Based on the object distance thus obtained, a focusinglens of a photographing lens of the camera is moved to a focus position.

Upon taking a picture using such an autofocusing camera, a photographermust adjust a distance measuring zone located at the center of the fieldof view of a finder to be coincident with the object to be photographed.Thereafter, the photographer first pushes the release switch down a halfstep to focus the focusing lens, and then fully pushes the releaseswitch down the full step to expose the film at the fixed camera angle.If a photographer wants to take a picture while making the focus pointcoincident with a portion of the field of view of a finder other thanthe center thereof, he or she must first adjust the object distancemeasuring zone located at the center of the field of view of a finder tobe coincident with an object. The photographer then pushes the releaseswitch down by a half step to lock the focus, and then change the cameraangle to obtain a desired composition of the picture in the finder. Whenthe desired composition is obtained, the release switch is pushed downby the full step to effect the exposure.

However, it is very difficult, particularly for a beginner, to move thecamera to the desired position while pushing the release switch by ahalf step. Furthermore, if the release switch, which has been pusheddown by a half step, is accidentally returned to the initial positionduring the movement of the camera, the focus lock is released, so thatthe object distance measuring must be effected again from the beginning,which is very troublesome.

SUMMARY OF THE INVENTION

The primary object of the present invention is to eliminate the drawbackof the prior art as mentioned above by providing an object distancemeasuring device of a camera in which the object distance of adesignated object in the field of view of the finder, can be measuredwithout moving the camera.

To achieve the object mentioned above, according to the presentinvention, there is provided an object distance measuring device in acamera, including an object distance measuring unit having a lightemitter which emits measuring light toward an object to be photographedand a light receiver which receives the measuring light as reflected bythe object; a direction varying mechanism for varying the direction ofthe object distance measuring unit, a measuring position varyingmechanism for varying the position of a measuring zone in a field ofview of a finder and an object distance measuring unit driving mechanismfor driving the object distance measuring unit to trace the movement ofthe measuring zone by the measuring position varying means, mechanismare provided to change the direction of the object distance measuringunit.

With this structure, the object distance of a designated object in thefield of view of the finder can be measured without moving the camera,so that the measuring position can be easily made coincident with theobject. Thus, no skill is required for the focusing operation.

According to another aspect of the present invention, there is providedan object distance measuring device in a camera, including an activeobject distance measuring mechanism for emitting measuring light towardan object to be photographed and receiving the measuring light asreflected by the object to detect the object distance measuring zone isprovided in a finder to indicate a measuring position at which themeasurement of the object distance by the active object distancemeasuring means is effected varying the position of the measuring zonein the finder, a mechanism for varying the measuring position measuredby the object distance measuring mechanism and a device for coincidingthe measuring zone in the finder and the measuring position of theactive object distance measuring mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described below in detail with reference to theaccompanying drawings, in which:

FIG. 1 is a block diagram of a main circuit of an object distancemeasuring device according to the present invention;

FIG. 2 is an enlarged perspective view of a main part of an objectdistance measuring device according to the present invention;

FIG. 3 is a front elevational view of FIG. 2;

FIG. 4 is a schematic view of a detecting mechanism of an objectdistance measuring zone mark according to the present invention;

FIG. 5 is a perspective view of a still video camera to which thepresent invention is applied;

FIG. 6A is a plan view of a position varying track ball, an X-directionmovable plate and a Y-direction movable plate, according to the presentinvention;

FIG. 6B is a front elevational view of FIG. 6A;

FIG. 6C is a side elevational view of FIG. 6B; and,

FIGS. 7 through 9 are schematic conceptual views for explaining theprinciple of the detection of a necessary angular displacement of anobject distance measuring unit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The illustrated non-limitative embodiment is directed to a still videocamera.

In FIG. 5, which shows the appearance of a still video camera 10 towhich the present invention is applied, a camera body 11 has aphotographing lens 12, a disc cover 13, a release switch 15, acompulsive strobe, light emitting button 16, a± EF switch (exposureadjusting switch) 17, a finder unit 20, an object distance measuringunit 21, and a position varying track ball 24. The position that theobject distance measuring unit 21; at the time that actual distancemeasuring is performed is defined as a measuring position. Also, thecamera body 11 has an indicating panel (not shown) which indicatesvarious photographing data, such as the number of tracks of a magneticdisc which have already been used to take pictures, an image pickupdevice as an image processing and recording system, and a driver whichdrives the magnetic disc, etc.

FIGS. 2 and 3 show, on an enlarged scale, the object distance measuringunit 21 and an emission direction varying mechanism 34 which rotates theobject distance measuring unit 21 about horizontal and vertical axesvary the direction of the emission of measuring light.

The object distance measuring unit 21 has a frame body 22 which isprovided on its upper and lower front portions with an infrared lightreceiver 25 and an infrared light emitter 23, respectively. The framebody 22 has a hollow portion 26 defined between the infrared lightemitter 23 and the infrared light receiver 25. The finder unit 20secured to the camera body 11 is inserted in the hollow portion 26. Theframe body 22 has pivot pins 27 and 29 on its side plates.

The emission direction varying mechanism 34 has frame body supportingbracket 30, a first motor 33 for rotating the frame body 22 about thehorizontal axis in a vertical plane and a second motor 37 for rotatingthe frame body 22 about a vertical axis in a horizontal plane. The framebody supporting bracket 30 has arms 30a and 30b which rotatably supportthe associated pivot pins 27 and 29. The frame body supporting bracket30 is provided on its lower surface with a pivot pin 31 which extends inthe vertical direction perpendicular to a line H connecting the axes ofthe pivot pins 27 and 29. The pivot pin 31 is held by the camera body 11so as to rotate the frame body supporting bracket 30 about the verticalaxis of the pivot pin 31 in a horizontal plane. Accordingly, as shown inarrows D and E in FIG. 3, the frame body 22 can rotate, to vary thedirection of the infrared light emitter 23 and the infrared lightreceiver 25. Thus the direction of the emission of the infraredmeasuring light varies in all directions.

The first motor 33 for rotating the frame body 22 about the horizontalaxis of the pivot pins 27 and 29 is attached to the rear-end of theframe body supporting bracket 30. The first motor 33 is provided on itsdrive shaft with a worm gear 35 secured thereto which is in mesh with aspur gear 32 secured to the pivot pin 27. The second motor 37 forrotating the frame body 22 about the vertical axis of the pivot pin 31is secured to the camera body 11 and has a worm gear 39 secured to adrive shaft thereof. The worm gear 39 is engaged by a spur gear 36secured to the pivot pin 31.

A position detecting device 28 is provided behind the finder unit 20, asshown in FIG. 4. The position detecting device 28 has an X-directionmovable plate 43 and a Y-direction movable plate 41. The X-directionmovable plate 43 is supported by pins 41 secured to the camera body 11so as to slide in the horizontal direction (X-direction in FIG. 2). TheX-direction movable plate 43 moves in the right- and left-handdirections X when the object distance measuring position varying trackball 24 rotates about a horizontal axis parallel with the optical axisof the photographing lens 12 in the vertical plane perpendicular to theoptical axis of the photographing lens 12.

The Y-direction movable plate 41 has an object distance measuring zonemark 40 at the center thereof and is supported by pins 45 secured to theX-direction movable plate 43 so as to move in the vertical X-directionperpendicular to the direction X in FIG. 2. The area which is delimitedby the finder zone mark 40 is defined as a measuring zone. TheY-direction movable plate 41 moves relative to the X-direction movableplate 43 in the vertical direction Y when the object distance measuringposition varying track ball 24 rotates about a horizontal axisperpendicular to the optical axis of the photographing lens 12 in thevertical plane parallel with the optical axis of the photographing lens12.

The camera body 11 has a code plate 46 having codes representing thedeviation xi (FIG. 9) of light in the direction X with respect to theoptical axis O of a finder lens 20a (FIG. 7). A position detecting brush47 is mounted to the X-direction movable plate 43 to come into contactwith the code plate 46 to detect the deviation xi.

The X-direction movable plate 43 has a code plate 49 having codesrepresenting the deviation yi (FIG. 9) of light in the direction Y withrespect to the optical axis O of a finder lens 20a. A position detectingbrush 50 is mounted to the Y-direction movable plate 41 to come intocontact with the code plate 49 to detect the deviation yi.

FIGS. 6A, 6B and 6C show the relationship between the X-directionmovable plate 43, the Y-direction movable plate 41 and the positionvarying track ball 24.

The position varying track ball 24 is rotatably fitted in a hole 55(FIG. 5) formed in the camera body 11. The camera body 11 has arotatable horizontal shaft 56 which extends in the forward and rearwarddirections of the camera body 11, i.e. in parallel with the optical axisof the finder lens 20a. The shaft 56 has a roller 57 which rotates aboutthe axis of the shaft 56 and a worm gear 59 secured to the shaft 56. Theroller 57 is in contact with the position varying track ball 24, so thatwhen the latter rotates about the axis parallel with the optical axis ofthe finder lens 20a in the clockwise and counterclockwise directions inFIG. 6B, the roller 57 rotates in the directions opposite thereto.

A rotatable vertical shaft 60 which extends in the vertical directionperpendicular to the shaft 56 is provided in the camera body 11. Thevertical shaft 60 is provided on its upper and lower ends with a sectorworm wheel 61 and a gear 63 which is in mesh with an X-direction rack 62provided on a corner of the X-direction movable plate 43 respectively.The worm wheel 61 engages with the worm gear 59, so that when theposition varying track ball 24 rotates in the clock wise andcounterclockwise directions in FIG. 6B, the worm wheel 61 moves in theforward and rearward directions of the camera body 11 through the wormgear 59. As a result, the gear 63 rotates to move the X-directionmovable plate 43 in the lateral direction of the camera body through theX-direction rack 62.

Similarly, the camera has a rotatable horizontal shaft 65 which extendsin the lateral direction perpendicular to the shaft 56 and the shaft 60and which is provided on its opposite ends with a rotatable sectormember 66 and a gear 67 secured thereto. The sector member 66 has anarched side face which is in contact with the position varying trackball 24. The gear 67 engages with a Y-direction track 69 mounted to acomer of the Y-direction movable plate 41. Consequently, when theposition varying track ball 24 rotates in the clockwise andcounterclockwise directions in FIG. 6C, perpendicular to the directionof the rotation thereof in FIG. 6B, the sector member 66 moves in theforward and rearward direction parallel with the optical axis of thefinder lens 20a. As a result, the rotation is transmitted to the rackthrough the shaft 65 and the gear 67, so that the Y-direction movableplate 41 moves in the upward and downward direction in FIG. 6C.

FIG. 1 shows a control circuit of an object distance measuring deviceaccording to the present invention.

To the input ports of the microcomputer 51 incorporated in the camerabody 11 are connected the light receiving element 25b (PSD: Positionsensitive device) of the infrared light receiver 25, the release switchthe compulsive strobe light emitting button 16, and the ±EF switch 17.Also, the X-direction detecting means 44 having the code plate 46 andthe position detecting brush 47, and the Y-direction detecting means 48having the code plate 49 and the position detecting brush 50 areconnected to the input ports of the microcomputer 51. The strobe 19, thelens driving means 71, the light emitting element 23b of the infraredlight emitter 23, the first motor 33 and the second motor 37 areconnected to the output ports of the microcomputer 51. The microcomputer51 includes an arithmetic operating i.e., calculating means 52 fordetermining the measuring position at which the measurement of theobject distance is effected, the motor driving means 53 and anarithmetic operating i.e., calculating means 70 for driving lens drivingmeans 71.

The arithmetic operating means 52 for determining the measuring positioncalculates the angular displacement θi of the object distance unit 20necessary for making it coincident with the distance measuring zone mark40, in accordance with the input data from the X-direction detectingmeans 44 and the Y-direction detecting means 48.

The motor driving means 53 rotates the first motor 33 and the secondmotor 37 in accordance with the result of the arithmetic operation ofthe arithmetic operating means 52. The motor driving means 53constitutes an object distance measuring unit controlling means,together with the arithmetic operating means 52 and the positiondetecting device 28.

The arithmetic operating means 70 calculates the object distance inaccordance with information from the light receiving element 25b and thedeviations xi and yi and outputs drive signals in accordance with thedistance data to the lens driving means 71 to drive the same thereby, tomove the focusing lens to the focus position.

The necessary angular displacement of the object distance measuring unit20 is determined, in accordance with respect to the optical axis O, asfollows.

As can be seen in FIGS. 7 and 8, if the angle θi (necessary angulardisplacement) of the light A incident upon an object deviated from theoptical axis O of the finder lens 20a with respect to the optical axis Ois very small, the following equation is obtained:

    yi=f×tanθi

    θi=tan.sup.-1 yi/f                                   (1)

wherein f is the focal length of the finder lens 20a: and,

yi is the deviation of the light A on an image plane from the opticalaxis O in the Y-direction.

Accordingly, the deviation yi can be converted to the angulardisplacement θi based on the equation (1) mentioned above. Thus, theobject distance measuring unit 21 is rotated in the direction Y by anangle θi with respect to the optical axis O, so that the distance of anobject deviated from the optical axis O by the deviation yi can bedetected. Similarly, the deviation xi on the image plane in thedirection X with respect to the optical axis O is electrically read(FIG. 9), and then the deviation xi is converted to the angulardisplacement θi of the object distance measuring unit 21 in thedirection X. Note that 25a in FIGS. 7 and 9 designates the lightreceiving lens of the infrared light receiver 25, and 23a the lightemitting lens of the infrared light emitter respectively.

Upon detecting the object distance, a photographer looks at the distancemeasuring zone mark 40 in the finder field of view through the finderunit 20 from the back of the camera body 11 in FIG. 5, i.e. from thedirection F in FIG. 2. If the zone mark 40 is located at the center ofthe field of view, so that there is no deviation of the object from theoptical axis O, the release switch 15 is pushed, down by a half step todetect the distance of the object, and then is pushed by a full step toeffect the exposure.

Conversely, if the object to be photographed is not to be located at thecenter of the field of view, so that the zone mark is not madecoincident with the object to be focused, the camera 10 is moved to adesired position in which the object which is intended to bephotographed is located in the field of view with a desired composition.Thereafter, the track ball 24 is rotated to make the zone mark 40coincident with the object. As a result, the measuring zone mark 40 ismoved in accordance with the direction of the rotation of the track ball24. The displacements of the measuring zone mark 40 in the X-directionand the Y-direction are detected by the Y-direction detecting means 48and the X-direction detecting means 44 which detect the positions of theY-direction movable plate 41 and the X-direction movable plate 43 in theY-direction and the X-direction, respectively.

The detected data of the Y-direction detecting means 48 and theX-direction detecting means 44 is input to the microcomputer 51, so thatthe necessary angle θi of the object distance measuring unit 21 in thedirections X and Y is calculated by the arithmetic operating means 52.The motor driving means 53 outputs the drive signals to the first andsecond motors 33 and 37 in accordance with the angular displacement θito rotate the object distance measuring unit 21 in the directions X andY. When the optical axis c of the light emitting lens 23a becomescoincident with the object with which the zone mark is made coincident,the object distance measuring unit 21 is stopped.

When the release switch 15 is pushed down a half step, the infraredlight is emitted from the light emitting element 23b toward the objectto be taken. The light reflected by the object is received by the lightreceiving element 25b. Thereafter, the arithmetic measuring operation ofthe object distance is commenced in accordance with the information fromthe light receiving element 25b and the deviations xi and yi by thearithmetic operating means 70 for driving the lens driving means 71.Thereafter, the lens driving means 71 is driven in accordance with thedata thus obtained by the arithmetic operation to move the focusing lensuntil the lens is focused. After that, focused the release switch 15 ispushed down a full step to actuate the shutter in order to expose animage of the object in the CCD. Thus, the image data of the object iswritten into a floppy disc loaded in the camera body through the disccover 13.

It is possible to memorize the stepped angular displacements θi of theobject distance measuring unit 21 which are preset to correspond to thedeviations xi and yi read from the code plates 46 and 49, for example ina ROM. In this alternative, the stored data can be directly read fromthe ROM in accordance with the movement of the zone mark 40 to move theobject distance measuring unit 21 without through the arithmeticoperating 10 means 52.

The present invention is not limited to the illustrated embodiments andcan be applied for example to a common still camera using a silver saltpicture.

Note that the terms "vertical" and "horizontal" referred to in thespecification mean the vertical and horizontal directions when thecamera is located in a normal position, that is, when the camera liessubstantially in a horizontal plane, as shown in FIG. 5.

We claim:
 1. An object distance measuring device in a camera,comprising:an object distance measuring unit having a light emitterwhich emits measuring light toward an object to be photographed and alight receiver which receives the measuring light as reflected by theobject; a direction varying mechanism for varying the direction of saidobject distance measuring unit; measuring position varying means forvarying the position of a measuring zone in a field of view finder; andobject distance measuring unit controlling means for controlling saidobject distance measuring unit to follow the movement of said measuringzone by said measuring position varying means, thereby to change thedirection of said object distance measuring unit.
 2. An object distancemeasuring device according to claim 1, wherein said light emittercomprises an infrared light emitting element.
 3. An object distancemeasuring device according to claim 1, wherein said light receivercomprises an infrared light receiving element.
 4. An object distancemeasuring device according to claim 3, wherein said light receivingelement is a position sensitive device.
 5. An object distance measuringdevice according to claim 1, wherein said object distance measuring unitcomprises a frame body which supports said light emitter said lightreceiver.
 6. An object distance measuring device according to claim 5,wherein said direction varying mechanism comprises a frame bodysupporting bracket which supports said frame body for rotation about.[.two orthogonal axes.]. .Iadd.a first axis .Iaddend., .[.and.]..Iadd.said frame body supporting bracket being rotatable about a secondaxis which is orthogonal to said first axis, a .Iaddend.a first.Iadd.motor for rotating said frame body about said firstaxis,.Iaddend.and .Iadd.a .Iaddend.second .[.motors.]. .Iadd.motor.Iaddend.for rotating said frame body supporting bracket .[.around thetwo orthogonal axes.]. .Iadd.and said frame body about said second axis.Iaddend..
 7. An object distance measuring device according to claim 1,wherein said measuring position varying means comprises a Y-directionmovable plate which is movable in a Y-direction and which includes saidmeasuring zone, and an X-direction movable plate which movably supportssaid Y-direction movable plate for movement in the Y-direction, saidX-direction movable plate is movable in an X-direction perpendicular tothe Y-direction, a driving force transmitting means for driving saidX-direction movable plate and said Y-direction movable plate, and aposition varying track ball which rotates to transmit the driving forceto said X-direction movable plate and said Y-direction movable plate. 8.An object distance measuring device according to claim 7, wherein saidmeasuring zone includes a zone mark which is provided on saidY-direction movable plate.
 9. An object distance measuring deviceaccording to claim 1, wherein said object distance measuring unitdriving means comprises a position detecting means for detecting theposition of said measuring zone, an arithmetic operating means forcalculating the angular displacement of said object distance measuringunit necessary for following said measuring zone in accordance with thedetected data of said position detecting means, and a driving means fordriving said object distance measuring unit in accordance with theresult of the arithmetic operation of said arithmetic operating means.10. An object distance measuring device according to claim 9, whereinsaid position detecting means comprises an X-direction detecting meansand a Y-direction detecting means which detect said measuringdisplacement of the zone in the X-direction and said Y-direction,respectively.
 11. An object distance measuring device according to claim10, further comprising a finder lens.
 12. An object distance measuringdevice according to claim 11, wherein said X-direction detecting meanscomprises a code plate having codes in accordance with the deviation ofan X-direction movable plate in an X-direction from said .[.;.]. opticalaxis of the finder lens and a position detecting brush which comes intocontact with said code plate to detect the deviation in the X-direction.13. An object distance measuring device according to claim 11, whereinsaid Y-direction detecting means comprises a code plate having codes inaccordance with the deviation of .[.an.]. .Iadd. a .Iaddend.Y-directionmovable plate in the Y-direction from said .[.and.]. optical axis of thefinder lens and a position detecting brush which comes into contact with.[.the.]. .Iadd.said .Iaddend.code plate to detect the deviation in theY-direction.
 14. In an object distance measuring device in a camera,including an active object distance measuring means for emittingmeasuring light toward an object to be photographed and receiving themeasuring light as reflected by the object to detect the objectdistance, and a measuring zone provided in a finder to indicate ameasuring position at which the measurement of the object distance bysaid active object distance measuring means is effected, said devicecomprising:means for varying the position of said measuring zone in saidfinder; means for varying the position measured by said active objectdistance measuring means; and means for coinciding said measuring zonein said finder and the measuring position of said active object distancemeasuring means.